1. Field of the Invention
This invention relates generally to a manufacturing process for the manufacture of semiconductor wafers. More specifically, this invention relates to a manufacturing process for the manufacture of semiconductor wafers including a method to minimize particulate induced clamping failures.
2. Discussion of the Related Art
The manufacturing process for the manufacture of semiconductor wafers includes many processes that are conducted in a chamber. The processes that are conducted in the chamber are typically conducted at different temperatures. Some of the processes conducted in the chamber are processes in which residual materials are deposited on the walls of the chamber. In many processes the wafers are held in place by placing them on an electrostatic chuck and the application of an electrical potential across the wafer and the chuck draws the wafer down to the surface of the chuck.
In the typical manufacturing process flow as shown in FIG. 1, the process steps that are to be conducted in a chamber starts as shown at 100. The temperature of the chamber is raised or lowered as required by the particular process that is to be conducted as indicated at 102. A production wafer is placed on an electrostatic chuck in the chamber as indicated at 104. The process is conducted as indicated at 106 and the production wafer is removed from the electrostatic chuck as indicated at 108 and the temperature of the chamber is raised or lowered as required for the next process as indicated at 110. The production wafer is then placed on the electrostatic chuck as indicated at 112 and the next process is conducted as shown at 114. This methodology continues until the process is finished as indicated at 116.
The problems with the prior art methodology just described are illustrated in FIGS. 2A & 2B. FIG. 2A shows a chamber 200 with an electrostatic chuck 202 in the chamber 200. The chamber 200 is undergoing a temperature change and therefore the electrostatic chuck 202 does not have a wafer clamped to it. The problem with the prior art process is that the residual materials deposited on the inside surface of the chamber have a different coefficient of expansion than the material from which the chamber is made. As the temperature of the chamber changes, the walls expand or contract causing flakes of residual material to break loose from the walls and fall on to the surface of the electrostatic chuck 202. Flakes of residual material on the walls of the chamber 200 are shown at 204 and flakes of residual material falling onto the electrostatic chuck 202 are shown at 206. Flakes on the surface of the electrostatic chuck 202 are indicated at 208. It should be appreciated that the problem associated with electrostatic chucks exist for other types of chucks on which residual flakes of material could fall and prevent a production wafer from being clamped flatly on the surface of the chuck.
FIG. 2B shows the problem caused by a flake or flakes 208 on the surface of the electrostatic chuck 202. The flake 208 prevents a wafer 210 from being completely clamped down on the surface of the electrostatic chuck 202. Because the criticality of dimensions in modem semiconductor integrated circuits, the non-flatness of the wafer 210 prevents the wafer from being properly processed. In order to rectify this situation, it is typically necessary to shut the chamber down, take the chamber out of service, open the chamber, and clean the surface of the electrostatic chuck. This cleaning process can take an entire workday because of the requirement to decrease the temperature of the chamber to a safe level and to ensure that any toxic materials will not contaminate the workplace environment.
Therefore, what is needed is a method of preventing flakes from a semiconductor-manufacturing chamber from preventing a wafer from lying flat on the surface of an electrostatic chuck in the chamber.